internal static async Task <LookupWithTask <TKey, TElement> > CreateAsync(IAsyncEnumerable <TElement> source, Func <TElement, CancellationToken, ValueTask <TKey> > keySelector, IEqualityComparer <TKey>?comparer, CancellationToken cancellationToken)
{
var lookup = new LookupWithTask <TKey, TElement>(comparer);
await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
var key = await keySelector(item, cancellationToken).ConfigureAwait(false);
lookup.GetOrCreateGrouping(key).Add(item);
}
return(lookup);
}
internal static async Task <LookupWithTask <TKey, TElement> > CreateForJoinAsync(IAsyncEnumerable <TElement> source, Func <TElement, CancellationToken, ValueTask <TKey> > keySelector, IEqualityComparer <TKey> comparer, CancellationToken cancellationToken)
{
var lookup = new LookupWithTask <TKey, TElement>(comparer);
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
var key = await keySelector(item, cancellationToken).ConfigureAwait(false);
if (key != null)
{
lookup.GetGrouping(key, create: true).Add(item);
}
}
return(lookup);
}
internal static async Task <LookupWithTask <TKey, TElement> > CreateAsync <TSource>(IAsyncEnumerable <TSource> source, Func <TSource, CancellationToken, ValueTask <TKey> > keySelector, Func <TSource, CancellationToken, ValueTask <TElement> > elementSelector, IEqualityComparer <TKey> comparer, CancellationToken cancellationToken)
{
Debug.Assert(source != null);
Debug.Assert(keySelector != null);
Debug.Assert(elementSelector != null);
var lookup = new LookupWithTask <TKey, TElement>(comparer);
await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
var key = await keySelector(item, cancellationToken).ConfigureAwait(false);
var group = lookup.GetGrouping(key, create: true);
var element = await elementSelector(item, cancellationToken).ConfigureAwait(false);
group.Add(element);
}
return(lookup);
}
public async ValueTask <bool> MoveNextAsync()
{
// nothing to do
if (!await _outer.MoveNextAsync().ConfigureAwait(false))
{
return(false);
}
if (_lookup == null)
{
_lookup = await Internal.LookupWithTask <TKey, TInner> .CreateForJoinAsync(_inner, _innerKeySelector, _comparer, _cancellationToken).ConfigureAwait(false);
}
var item = _outer.Current;
var outerKey = await _outerKeySelector(item, _cancellationToken).ConfigureAwait(false);
var inner = _lookup[outerKey].ToAsyncEnumerable();
Current = await _resultSelector(item, inner, _cancellationToken).ConfigureAwait(false);
return(true);
}
protected override async ValueTask <bool> MoveNextCore()
{
switch (_state)
{
case AsyncIteratorState.Allocated:
_outerEnumerator = _outer.GetAsyncEnumerator(_cancellationToken);
_mode = State_If;
_state = AsyncIteratorState.Iterating;
goto case AsyncIteratorState.Iterating;
case AsyncIteratorState.Iterating:
switch (_mode)
{
case State_If:
if (await _outerEnumerator.MoveNextAsync().ConfigureAwait(false))
{
_lookup = await Internal.LookupWithTask <TKey, TInner> .CreateForJoinAsync(_inner, _innerKeySelector, _comparer, _cancellationToken).ConfigureAwait(false);
if (_lookup.Count != 0)
{
_mode = State_DoLoop;
goto case State_DoLoop;
}
}
break;
case State_DoLoop:
_item = _outerEnumerator.Current;
var g = _lookup.GetGrouping(await _outerKeySelector(_item, _cancellationToken).ConfigureAwait(false), create: false);
if (g != null)
{
_count = g._count;
_elements = g._elements;
_index = 0;
_mode = State_For;
goto case State_For;
}
// advance to while
_mode = State_While;
goto case State_While;
case State_For:
_current = await _resultSelector(_item, _elements[_index], _cancellationToken).ConfigureAwait(false);
_index++;
if (_index == _count)
{
_mode = State_While;
}
return(true);
case State_While:
var hasNext = await _outerEnumerator.MoveNextAsync().ConfigureAwait(false);
if (hasNext)
{
goto case State_DoLoop;
}
break;
}
await DisposeAsync().ConfigureAwait(false);
break;
}
return(false);
}
